Effects of caloric restriction and different diet types on weight loss, metabolic profile and behavior of overweight and obese dogs.

The nutritional composition of the diet and food choices can influence weight loss program outcomes, although caloric deficit remains the main strategy for reducing body fat. This study compared weight loss, hematological parameters, biochemical profile, and behavior of overweight and obese dogs (n = 34) fed under caloric restriction using commercial dry food (n = 9), homemade food (n = 9), or mixed feeding (n = 16). Each dog was monitored for approximately three months (104 days) with monthly consultations for clinical evaluation, caloric intake adjustments, blood collection, and morphometric measurements. Initial metabolizable energy was calculated based on resting energy requirement using the formula 70 kcal × (kg BW⁰·⁷⁵). All diet groups achieved similar body weight loss (4.5%) under caloric restriction, regardless of diet type. Although most biochemical and hematological parameters showed no differences between diets, serum triglycerides were lower in the homemade food group despite this formulation presenting higher fat content. Additionally, HDL concentrations increased over time regardless of diet type. These findings suggest that moderate caloric restriction can promote weight loss and influence lipid metabolism after 104 days. Behavioral assessments based on owner questionnaires revealed differences among dietary groups in physical disposition, social behavior, and food-seeking patterns. Dogs fed mixed diets showed higher frequencies of fatigue, difficulty running or climbing stairs, and reduced play at home. Most dogs were described as joyful and interested in walks, though the majority were considered only moderately active. Overall, despite differences in behavioral patterns across diets, the average weight loss was not sufficient to promote marked functional or behavioral improvements.